Evaluation of repolarization dynamics using the QT-RR regression line slope and intercept relationship during 24-h...

QT-RR linear regression consists of two parameters, slope and intercept, and the aim of this study was to evaluate repolarization dynamics using the QT-RR linear regression slope and intercept relationship during 24-h Holter ECG. This study included 466 healthy subjects (54.6 ± 14.6 years; 200 men and 266 women) and 17 patients with ventricular arrhythmias, consisted of 10 patients with idiopathic ventricular fibrillation (IVF) and 7 patients with torsades de pointes (TDP). QT and RR intervals were measured from ECG waves based on a 15-s averaged ECG during 24-h Holter recording using an automatic QT analyzing system. The QT interval dependence on the RR interval was analyzed using a linear regression line for each subject ([QT] = A[RR] + B; where A is the slope and B is the y-intercept). The slope of the QT-RR regression line in healthy subjects was significantly greater in women than in men (0.185 ± 0.036 vs. 0.161 ± 0.033, p < 0.001) and the intercept was significantly smaller in women than in men (0.229 ± 0.028 vs. 0.240 ± 0.027, p < 0.001). A scatter diagram of the QT-RR regression line slope and intercept among healthy subjects demonstrated a statistically significant negative correlation (B = -0.62A + 0.34, r = -0.79). Distribution of both scatter diagrams of the slope and the intercept of the QT-RR regression line in patients with IVF and TDP was different from healthy subjects (left corner for IVF and upward shift for TDP). The slope and intercept relationship of the QT-RR linear regression line based on 24-h Holter ECG may become a simple useful marker for abnormality of ventricular repolarization dynamics.